1892-S Morgan

as supedave says probably recovering from an old cleaning (probably pretty harsh by the look of it).

The colors are atractive and sort of what you might find on a single sided toned Morgan, usually from an original bag where one side is in contact with the canvas bag, probably in the storage life of 6-8 decades. Those types of toning will literally jump out at you they are so vivid and natural. You can see some examples in Wyane Miller's excellent "An Analysis of Morgan and Peace dollars" book. I also recently ran across this website with some "out of this world" examples of monster toned dollars.

http://www.jhonecash.com/coins/tonedmorgans.asp

I've seen a similar look on your dollar that comes from baking it in a potato, seriously! In rainbow toned coins the formula for a great candidate for real toning the progression is yellow-magenta-cyan and it can repeat, it will not go in a different order in colors, that is nature. AT will mix these values up through various chemicals or surface alterations to the coin when applying. Some AT coins do find their way into TPG holders and they are generally market acceptable errors. I've found almost all rainbow toned dollars on ebay the past few years are AT and not original if uncertified. Nefarious coin doctors at work.

I still like your dollar though, cool color is always an attention getter. I used a few wild AT coins in my bourse case, when I was dealing at shows, to show off what to look for and they always elicited comments when I had them next to my favorite real toned dollars. The end roll coins, I personally, love the flaps and lines caused by sulpur content wrapper paper over decades of time.

I agree with EF-40/45. Like the previous posters, I have my doubts about the toning.

my first impression when I saw this coin was EF-40

take a junk merc and put it in an iron skillet and see if it turns blue on the upside and tanish on the down.

Looks like artificial toning to me.